UART connection jumper for UPDI

[nerdralph]

The CH330N could be used for UPDI programming.
https://github.com/mraardvark/pyupdi

If you made the UPDI connector 4 pins, with the 4th pin wired to the CH330N Tx/Rx + 4k7 resistor, a jumper could be used for UPDI programming with the CH330 by connecting pins 3 & 4.

[wagiminator]

That's a great idea. When I designed the boards, I didn't know pyupdi yet. Recently I made a pyupdi based on the CH330N: https://github.com/wagiminator/AVR-Programmer/tree/master/PyUPDI_Programmer.